iio: pressure: bmp280: add humidity support

Enable humidity support for the BME280 part
Signed-off-by: Matt Ranostay <matt.ranostay@intel.com>
Acked-by: Vlad Dogaru <vlad.dogaru@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/pressure/Kconfig

@@ -12,7 +12,8 @@ config BMP280
 	select REGMAP_I2C
 	help
 	  Say yes here to build support for Bosch Sensortec BMP180 and BMP280
-	  pressure and temperature sensors.
+	  pressure and temperature sensors. Also supports the BE280 with
+	  an additional humidty sensor channel.
 
 	  To compile this driver as a module, choose M here: the module
 	  will be called bmp280.

drivers/iio/pressure/bmp280.c

@@ -10,6 +10,7 @@
  * Datasheet:
  * https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BMP180-DS000-121.pdf
  * https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BMP280-DS001-12.pdf
+ * https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BME280_DS001-11.pdf
  */
 
 #define pr_fmt(fmt) "bmp280: " fmt
@@ -23,6 +24,8 @@
 #include <linux/iio/sysfs.h>
 
 /* BMP280 specific registers */
+#define BMP280_REG_HUMIDITY_LSB		0xFE
+#define BMP280_REG_HUMIDITY_MSB		0xFD
 #define BMP280_REG_TEMP_XLSB		0xFC
 #define BMP280_REG_TEMP_LSB		0xFB
 #define BMP280_REG_TEMP_MSB		0xFA
@@ -31,7 +34,17 @@
 #define BMP280_REG_PRESS_MSB		0xF7
 
 #define BMP280_REG_CONFIG		0xF5
+#define BMP280_REG_CTRL_MEAS		0xF4
 #define BMP280_REG_STATUS		0xF3
+#define BMP280_REG_CTRL_HUMIDITY	0xF2
+
+/* Due to non linear mapping, and data sizes we can't do a bulk read */
+#define BMP280_REG_COMP_H1		0xA1
+#define BMP280_REG_COMP_H2		0xE1
+#define BMP280_REG_COMP_H3		0xE3
+#define BMP280_REG_COMP_H4		0xE4
+#define BMP280_REG_COMP_H5		0xE5
+#define BMP280_REG_COMP_H6		0xE7
 
 #define BMP280_REG_COMP_TEMP_START	0x88
 #define BMP280_COMP_TEMP_REG_COUNT	6
@@ -46,6 +59,15 @@
 #define BMP280_FILTER_8X		(BIT(3) | BIT(2))
 #define BMP280_FILTER_16X		BIT(4)
 
+#define BMP280_OSRS_HUMIDITY_MASK	(BIT(2) | BIT(1) | BIT(0))
+#define BMP280_OSRS_HUMIDITIY_X(osrs_h)	((osrs_h) << 0)
+#define BMP280_OSRS_HUMIDITY_SKIP	0
+#define BMP280_OSRS_HUMIDITY_1X		BMP280_OSRS_HUMIDITIY_X(1)
+#define BMP280_OSRS_HUMIDITY_2X		BMP280_OSRS_HUMIDITIY_X(2)
+#define BMP280_OSRS_HUMIDITY_4X		BMP280_OSRS_HUMIDITIY_X(3)
+#define BMP280_OSRS_HUMIDITY_8X		BMP280_OSRS_HUMIDITIY_X(4)
+#define BMP280_OSRS_HUMIDITY_16X	BMP280_OSRS_HUMIDITIY_X(5)
+
 #define BMP280_OSRS_TEMP_MASK		(BIT(7) | BIT(6) | BIT(5))
 #define BMP280_OSRS_TEMP_SKIP		0
 #define BMP280_OSRS_TEMP_X(osrs_t)	((osrs_t) << 5)
@@ -92,6 +114,7 @@
 
 #define BMP180_CHIP_ID			0x55
 #define BMP280_CHIP_ID			0x58
+#define BME280_CHIP_ID			0x60
 #define BMP280_SOFT_RESET_VAL		0xB6
 
 struct bmp280_data {
@@ -103,6 +126,7 @@ struct bmp280_data {
 	/* log of base 2 of oversampling rate */
 	u8 oversampling_press;
 	u8 oversampling_temp;
+	u8 oversampling_humid;
 
 	/*
 	 * Carryover value from temperature conversion, used in pressure
@@ -120,9 +144,13 @@ struct bmp280_chip_info {
 	const int *oversampling_press_avail;
 	int num_oversampling_press_avail;
 
+	const int *oversampling_humid_avail;
+	int num_oversampling_humid_avail;
+
 	int (*chip_config)(struct bmp280_data *);
 	int (*read_temp)(struct bmp280_data *, int *);
 	int (*read_press)(struct bmp280_data *, int *, int *);
+	int (*read_humid)(struct bmp280_data *, int *, int *);
 };
 
 /*
@@ -143,12 +171,18 @@ static const struct iio_chan_spec bmp280_channels[] = {
 		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
 				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
 	},
+	{
+		.type = IIO_HUMIDITYRELATIVE,
+		.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
+				      BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO),
+	},
 };
 
 static bool bmp280_is_writeable_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
 	case BMP280_REG_CONFIG:
+	case BMP280_REG_CTRL_HUMIDITY:
 	case BMP280_REG_CTRL_MEAS:
 	case BMP280_REG_RESET:
 		return true;
@@ -160,6 +194,8 @@ static bool bmp280_is_writeable_reg(struct device *dev, unsigned int reg)
 static bool bmp280_is_volatile_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
+	case BMP280_REG_HUMIDITY_LSB:
+	case BMP280_REG_HUMIDITY_MSB:
 	case BMP280_REG_TEMP_XLSB:
 	case BMP280_REG_TEMP_LSB:
 	case BMP280_REG_TEMP_MSB:
@@ -177,13 +213,77 @@ static const struct regmap_config bmp280_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 
-	.max_register = BMP280_REG_TEMP_XLSB,
+	.max_register = BMP280_REG_HUMIDITY_LSB,
 	.cache_type = REGCACHE_RBTREE,
 
 	.writeable_reg = bmp280_is_writeable_reg,
 	.volatile_reg = bmp280_is_volatile_reg,
 };
 
+/*
+ * Returns humidity in percent, resolution is 0.01 percent. Output value of
+ * "47445" represents 47445/1024 = 46.333 %RH.
+ *
+ * Taken from BME280 datasheet, Section 4.2.3, "Compensation formula".
+ */
+
+static u32 bmp280_compensate_humidity(struct bmp280_data *data,
+				      s32 adc_humidity)
+{
+	struct device *dev = &data->client->dev;
+	unsigned int H1, H3, tmp;
+	int H2, H4, H5, H6, ret, var;
+
+	ret = regmap_read(data->regmap, BMP280_REG_COMP_H1, &H1);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H1 comp value\n");
+		return ret;
+	}
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H2, &tmp, 2);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H2 comp value\n");
+		return ret;
+	}
+	H2 = sign_extend32(le16_to_cpu(tmp), 15);
+
+	ret = regmap_read(data->regmap, BMP280_REG_COMP_H3, &H3);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H3 comp value\n");
+		return ret;
+	}
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H4, &tmp, 2);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H4 comp value\n");
+		return ret;
+	}
+	H4 = sign_extend32(((be16_to_cpu(tmp) >> 4) & 0xff0) |
+			  (be16_to_cpu(tmp) & 0xf), 11);
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_H5, &tmp, 2);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H5 comp value\n");
+		return ret;
+	}
+	H5 = sign_extend32(((le16_to_cpu(tmp) >> 4) & 0xfff), 11);
+
+	ret = regmap_read(data->regmap, BMP280_REG_COMP_H6, &tmp);
+	if (ret < 0) {
+		dev_err(dev, "failed to read H6 comp value\n");
+		return ret;
+	}
+	H6 = sign_extend32(tmp, 7);
+
+	var = ((s32)data->t_fine) - 76800;
+	var = ((((adc_humidity << 14) - (H4 << 20) - (H5 * var)) + 16384) >> 15)
+		* (((((((var * H6) >> 10) * (((var * H3) >> 11) + 32768)) >> 10)
+		+ 2097152) * H2 + 8192) >> 14);
+	var -= ((((var >> 15) * (var >> 15)) >> 7) * H1) >> 4;
+
+	return var >> 12;
+};
+
 /*
  * Returns temperature in DegC, resolution is 0.01 DegC.  Output value of
  * "5123" equals 51.23 DegC.  t_fine carries fine temperature as global
@@ -324,6 +424,34 @@ static int bmp280_read_press(struct bmp280_data *data,
 	return IIO_VAL_FRACTIONAL;
 }
 
+static int bmp280_read_humid(struct bmp280_data *data, int *val, int *val2)
+{
+	int ret;
+	__be16 tmp = 0;
+	s32 adc_humidity;
+	u32 comp_humidity;
+
+	/* Read and compensate temperature so we get a reading of t_fine. */
+	ret = bmp280_read_temp(data, NULL);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_bulk_read(data->regmap, BMP280_REG_HUMIDITY_MSB,
+			       (u8 *) &tmp, 2);
+	if (ret < 0) {
+		dev_err(&data->client->dev, "failed to read humidity\n");
+		return ret;
+	}
+
+	adc_humidity = be16_to_cpu(tmp);
+	comp_humidity = bmp280_compensate_humidity(data, adc_humidity);
+
+	*val = comp_humidity;
+	*val2 = 1024;
+
+	return IIO_VAL_FRACTIONAL;
+}
+
 static int bmp280_read_raw(struct iio_dev *indio_dev,
 			   struct iio_chan_spec const *chan,
 			   int *val, int *val2, long mask)
@@ -336,6 +464,9 @@ static int bmp280_read_raw(struct iio_dev *indio_dev,
 	switch (mask) {
 	case IIO_CHAN_INFO_PROCESSED:
 		switch (chan->type) {
+		case IIO_HUMIDITYRELATIVE:
+			ret = data->chip_info->read_humid(data, val, val2);
+			break;
 		case IIO_PRESSURE:
 			ret = data->chip_info->read_press(data, val, val2);
 			break;
@@ -349,6 +480,10 @@ static int bmp280_read_raw(struct iio_dev *indio_dev,
 		break;
 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
 		switch (chan->type) {
+		case IIO_HUMIDITYRELATIVE:
+			*val = 1 << data->oversampling_humid;
+			ret = IIO_VAL_INT;
+			break;
 		case IIO_PRESSURE:
 			*val = 1 << data->oversampling_press;
 			ret = IIO_VAL_INT;
@@ -372,6 +507,23 @@ static int bmp280_read_raw(struct iio_dev *indio_dev,
 	return ret;
 }
 
+static int bmp280_write_oversampling_ratio_humid(struct bmp280_data *data,
+					       int val)
+{
+	int i;
+	const int *avail = data->chip_info->oversampling_humid_avail;
+	const int n = data->chip_info->num_oversampling_humid_avail;
+
+	for (i = 0; i < n; i++) {
+		if (avail[i] == val) {
+			data->oversampling_humid = ilog2(val);
+
+			return data->chip_info->chip_config(data);
+		}
+	}
+	return -EINVAL;
+}
+
 static int bmp280_write_oversampling_ratio_temp(struct bmp280_data *data,
 					       int val)
 {
@@ -417,6 +569,9 @@ static int bmp280_write_raw(struct iio_dev *indio_dev,
 	case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
 		mutex_lock(&data->lock);
 		switch (chan->type) {
+		case IIO_HUMIDITYRELATIVE:
+			ret = bmp280_write_oversampling_ratio_humid(data, val);
+			break;
 		case IIO_PRESSURE:
 			ret = bmp280_write_oversampling_ratio_press(data, val);
 			break;
@@ -535,6 +690,37 @@ static const struct bmp280_chip_info bmp280_chip_info = {
 	.read_press = bmp280_read_press,
 };
 
+static int bme280_chip_config(struct bmp280_data *data)
+{
+	int ret = bmp280_chip_config(data);
+	u8 osrs = BMP280_OSRS_HUMIDITIY_X(data->oversampling_humid + 1);
+
+	if (ret < 0)
+		return ret;
+
+	return regmap_update_bits(data->regmap, BMP280_REG_CTRL_HUMIDITY,
+				  BMP280_OSRS_HUMIDITY_MASK, osrs);
+}
+
+static const struct bmp280_chip_info bme280_chip_info = {
+	.regmap_config = &bmp280_regmap_config,
+
+	.oversampling_temp_avail = bmp280_oversampling_avail,
+	.num_oversampling_temp_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
+	.oversampling_press_avail = bmp280_oversampling_avail,
+	.num_oversampling_press_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
+	.oversampling_humid_avail = bmp280_oversampling_avail,
+	.num_oversampling_humid_avail = ARRAY_SIZE(bmp280_oversampling_avail),
+
+	.chip_config = bme280_chip_config,
+	.read_temp = bmp280_read_temp,
+	.read_press = bmp280_read_press,
+	.read_humid = bmp280_read_humid,
+};
+
+
 static bool bmp180_is_writeable_reg(struct device *dev, unsigned int reg)
 {
 	switch (reg) {
@@ -849,21 +1035,29 @@ static int bmp280_probe(struct i2c_client *client,
 	indio_dev->dev.parent = &client->dev;
 	indio_dev->name = id->name;
 	indio_dev->channels = bmp280_channels;
-	indio_dev->num_channels = ARRAY_SIZE(bmp280_channels);
 	indio_dev->info = &bmp280_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
 	switch (id->driver_data) {
 	case BMP180_CHIP_ID:
+		indio_dev->num_channels = 2;
 		data->chip_info = &bmp180_chip_info;
 		data->oversampling_press = ilog2(8);
 		data->oversampling_temp = ilog2(1);
 		break;
 	case BMP280_CHIP_ID:
+		indio_dev->num_channels = 2;
 		data->chip_info = &bmp280_chip_info;
 		data->oversampling_press = ilog2(16);
 		data->oversampling_temp = ilog2(2);
 		break;
+	case BME280_CHIP_ID:
+		indio_dev->num_channels = 3;
+		data->chip_info = &bme280_chip_info;
+		data->oversampling_press = ilog2(16);
+		data->oversampling_humid = ilog2(16);
+		data->oversampling_temp = ilog2(2);
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -895,6 +1089,7 @@ static const struct acpi_device_id bmp280_acpi_match[] = {
 	{"BMP0280", BMP280_CHIP_ID },
 	{"BMP0180", BMP180_CHIP_ID },
 	{"BMP0085", BMP180_CHIP_ID },
+	{"BME0280", BME280_CHIP_ID },
 	{ },
 };
 MODULE_DEVICE_TABLE(acpi, bmp280_acpi_match);
@@ -903,6 +1098,7 @@ static const struct i2c_device_id bmp280_id[] = {
 	{"bmp280", BMP280_CHIP_ID },
 	{"bmp180", BMP180_CHIP_ID },
 	{"bmp085", BMP180_CHIP_ID },
+	{"bme280", BME280_CHIP_ID },
 	{ },
 };
 MODULE_DEVICE_TABLE(i2c, bmp280_id);